Method of driving display apparatus and display apparatus

ABSTRACT

A display apparatus according to the present invention is provided with a matrix-type liquid crystal panel and a switching liquid crystal panel, the matrix-type liquid crystal panel and the switching liquid crystal panel assembled together. In the display apparatus, a polarity of a voltage applied on an electrode pair of the switching liquid crystal panel is inverted once in substantially one vertical period or in one or more vertical period. With this arrangement, it is possible to reduce a number of bright line or dark line. This attains display quality improvement and power consumption reduction.

This Nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2004/067222 filed in Japan on Mar. 10, 2004,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method of driving (addressing) adisplay apparatus (for use in OA (Office Automation) apparatus, AV(Audio Visual) apparatus, and the like apparatus) having a structure inwhich a liquid crystal panel and a matrix-type image display means areassembled together, and to the display apparatus.

BACKGROUND OF THE INVENTION

A display apparatus having a structure in which a liquid crystal panelis provided is conventionally well known as one type of matrix-typedisplay apparatus. One example of such a display apparatus is one havinga structure in which a dot-matrix-type display apparatus (for example,M-row/N-column active matrix liquid crystal panel) is assembled togetherwith a liquid crystal panel for switching two-dimensional (2-D) displayand three-dimensional (3-D) display (hereinafter, this kind of liquidcrystal panel is referred to as a switching liquid crystal panel), andbeing able to electrically switching the two-dimensional display and thethree-dimensional display (e.g. see Publication of Japanese PatentApplication, Tokukaihei, publication No. 3-119889 (published on May 22,1991).

FIGS. 12 and 13 illustrates cross sections of a panel section of theliquid crystal display apparatus for dual-display of two-dimensional andthree-dimensional images. FIG. 12 illustrates the cross section of thepanel section when the three-dimensional image is displayed. FIG. 13illustrates the cross section of the panel section when thetwo-dimensional image is displayed. As illustrated in FIGS. 12 and 13,the liquid crystal display apparatus for dual-display of thetwo-dimensional image and the three-dimensional image is provided with adot-matrix type liquid crystal panel 101 and a switching liquid crystalpanel 102 assembled together.

The dot-matrix liquid crystal panel 101 is provided with a polarizer111, a counter electrode 112, a liquid crystal layer 113, a pixelelectrode 114, and a polarizer 115, which are arranged in lamination.The pixel electrode 114 is provided with an active element (notillustrated). The active element is turned ON/OFF in accordance with ascanning signal inputted from a scanning electrode control circuit (notillustrated). When the active element is ON, a video signal is inputtedfrom a video signal control circuit (not illustrated) into the pixelelectrode 114. In other words, the dot-matrix type liquid crystal panel101 serves as display image generating means for generating a displayedscreen in accordance with image data.

The switching liquid crystal panel 102 is provided with a patternedretardation film 121, an upper electrode 122, a liquid crystal layer123, a lower electrode 124, and a polarizer 125, which are arranged inlamination. According to whether or not a voltage is applied on theliquid crystal layer 123, the switching liquid crystal panel 102switches over whether a parallax barrier is present or absent (i.e.whether the parallax barrier is effectuated or not).

The upper electrode 122 and the lower electrode 124 are connected with apower source circuit (not illustrated) for applying a driving voltage onthese electrodes. In accordance with whether the two-dimensional imageor the three-dimensional image is to be displayed, the power sourcecircuit switches over whether it supplies the voltage or not. Forinstance, the voltage applications switches over the display to thetwo-dimensional image display. On the other hand, when no voltageapplication is made, the display is switched over to thethree-dimensional image display. In accordance with whether or not thevoltage is applied on the upper electrode 122 and the lower electrode124, the polarization state of light passing through the liquid crystallayer 123 is switched over.

The patterned retardation film 121 has two types of regions 121A and121B, which are in a stripe shape and in alternative arrangement. Thetwo types of regions 121A and 121B have different polarization states.The light having passed through the liquid crystal layer 123 enters thepatterned retardation film 121. The regions 121A and 121B of thepatterned retardation film 121 have different rubbing directions. Inother words, their slow axes are in different directions. Therefore,light having passed through the region 121A and light having passedthrough the region 121B have different polarization state. For instance,it is designed that a polarization axis of the light having passedthrough the region 121A and that of the light having passed through theregion 121B make 90 degrees.

The polarization states of the light having passed through the regions121A and 121B depend on the polarization state of the light incident onthe patterned retardation film 121, that is, the polarization state ofthe light having passed through the liquid crystal layer 123. The lighthaving passed through the patterned retardation film 121 enter thepolarizer 115 of the dot-matrix type liquid crystal panel 101.

When the image is displayed as a three-dimensional image, that is, whenno voltage is applied on the liquid crystal layer 123, an optical axisof the light having passed through the region 121A is parallel with atransmission axis of the polarizer 115, but an optical axis of the lighthaving passed through the region 121B is perpendicular to thetransmission axis of the polarizer 115.

In other words, as illustrated in FIG. 12, the patterned retardationfilm 121, working together with the polarizer 115, causes optical effectthereby effectuating functions of a parallax barrier. The regions 121Aof the patterned retardation film 121 servers as a transmission region,while the region 121B serves as a blocking region.

Light having passed through the region 121A and the polarizer 115 andtraveling toward a right eye (i.e. in a right-eye direction) passesthrough that part of the liquid crystal layer 113 on which the voltageis applied by a pixel electrode 114R that is for displaying inaccordance with image data for the right eye (hereinafter, this imagedata is referred to as right-eye image data). On the other hand, lighthaving passed through the region 121A and the polarizer 115 andtraveling toward a left eye (i.e. in a left-eye direction) passesthrough that part of the liquid crystal layer 113 on which the voltageis applied by a pixel electrode 114L that is for displaying inaccordance with image data for the left eye (hereinafter, this imagedata is referred to as left-eye image data). The left-eye image data andthe right-eye image data are for images which are to be viewed fromdifferent observation positions. The display image displayed inaccordance with the right-eye image data is viewed with the right eyewhile the display image displayed in accordance with the left-eye imagedata is viewed with the left eye. In this way, the display image isrecognized as a three-dimensional image.

On the other hand, when the image is displayed as a two-dimensionalimage, that is, when the voltage is applied on the liquid crystal layer123, light having passed through the region 121A and light having passedthrough the region 121B are such that the optical axes thereof aresymmetrically tilted from the transmission axis of the polarizer 115.

That is, both of the light having passed through the regions 121A andthe regions 121B pass through the polarizer with the same transmittance,thereby not effectuating the function of the parallax barrier. Thus, theimage from all the pixels are viewed with the both right and left eyes,thereby allowing the display of the two-dimensional image.

Whether the parallax barrier is effectuated or not is switched over bywhether or not applying the voltage on the liquid crystal layer 123 ofthe switching liquid crystal panel 102, thereby switching over betweenthe two-dimensional image display and the three-dimensional imagedisplay.

The liquid crystal display apparatus for dual-use in displaying thetwo-dimensional image and the three-dimensional image is arranged suchthat the voltages to be applied on the liquid crystal layers 113 and the123 of the dot-matrix type liquid crystal panel 101 and the switchingliquid crystal panel 102 are inverted in polarity in order to preventdeterioration of display quality. Control circuits respectively controlstiming of the polarity inversion of the dot-matrix type liquid crystalpanel 101 and the switching liquid crystal panel 102.

Further, a power source circuit for generating the voltage to besupplied to the dot-matrix type liquid crystal panel 101 has a differentconfiguration from that of a power source circuit for generating thevoltage to be supplied to the switching liquid crystal panel 102.

In the conventional arrangements, however, no attention is paid to acycle of the timing of the polarity inversion of the switching liquidcrystal panel 102. Thus, the timing of the polarity inversion is not insynchronism with a vertical cycle of the dot-matrix type liquid crystalpanel 101. Moreover, in some cases, the polarity inversion cycle isextremely shorter than the vertical cycle of the dot-matrix type liquidcrystal panel 101.

The inventors of the present invention noted the significance of thetiming of the polarity inversion of the switching liquid crystal panel102, and a problem associated with the timing of the polarity inversion:the timing may cause display quality deterioration. This problem isexplained below.

A position of a polarity inversion point of the switching liquid crystalpanel 102 with respect to a vertical display starting point is changedif the timing of the polarity inversion of the switching liquid crystalpanel 102 is not in synchronism with the vertical cycle of thedot-matrix type liquid crystal panel 101.

Moreover, the polarity of the switching liquid crystal panel 102 isinverted in plural times within an effective display period of thedot-matrix type liquid crystal panel 101, if the polarity inversioncycle of the switching liquid crystal panel 102 is extremely shorterthan the vertical cycle.

FIG. 14 illustrates waveforms of the voltage applied on the dot-matrixtype liquid crystal panel 101 and the switching liquid crystal panel 102in the conventional arrangement. In FIG. 14, the upper waveformrepresents the vertical display start signal of the dot-matrix typeliquid crystal panel 101. The middle waveform is a waveform of thevoltage applied on the pixel electrode 114 of the dot-matrix type liquidcrystal panel 101. The lower waveform is a waveform of the voltageapplied on the switching liquid crystal panel 102.

As illustrated in FIG. 14, one vertical period has the effective displayperiod and blanking period: the voltage is applied on the pixelelectrodes on 1 to N lines (i.e. 1 to N rows) in the effective displayperiod; and the blanking period is a rest of the one vertical period. InFIG. 14, the polarity of the switching liquid crystal panel 102 isinverted four times in the effective display period.

Moreover, it can be understood from FIG. 14 that the polarity inversionof the switching liquid crystal panel 102 in accordance with thevertical display start signal occurs at different points in respectivevertical periods.

The inventors of the present inventions found out that, due to capacitycoupling occurred between the upper electrode 122 of the switchingliquid crystal panel 102 and pixel electrode 114 of the dot-matrix typeliquid crystal panel 101, an video signal to be inputted in the pixelelectrode 114 is fluctuated in accordance with the inversion of thevoltage applied on the switching liquid crystal panel 102, thefluctuation taking place at the timing of polarity inversion of thevoltage applied on the switching liquid crystal panel 102.

FIG. 15 illustrates a waveform of the video signal when the voltageapplied on the switching liquid crystal panel 102 is inverted.

As illustrated in FIG. 15, at a timing a at which the voltage applied onthe switching liquid crystal panel 102 (i.e. the voltage between theupper electrode 122 and the lower electrode 124) is inverted from thenegative polarity to the positive polarity, the video signal is shiftedtoward a positive direction. On the other hand, as a timing b at whichthe voltage is inverted from the positive polarity to the negativepolarity, the video signal is shifted toward a negative direction.

Therefore, a pixel electrode whose active element is ON at the timing ais excessively charged when the video signal is a signal shifted to thepositive direction. On the other hand, this pixel electrode is notsufficiently charged when the video signal is a signal shifted to thenegative direction. Moreover, a pixel electrode whose active element isON at the timing b is not sufficiently charged when the video signal isa signal shifted to the positive direction. On the other hand, thispixel electrode is excessively charged when the video signal is a signalshifted to the negative direction.

The excess charging on the pixel electrode causes a dark line on thedisplayed screen. Moreover, the insufficient charging on the pixelelectrode causes a bright line on the displayed screen.

Therefore, if the polarity of the switching liquid crystal panel 102 isinverted in plural times within one effective display period asdescribed above, a plurality of bright lines or dark lines appear,causing display deterioration. Further, in case where the polarityinversion point of the inversion carried out in accordance with thevertical display start signal is changed per vertical period, the brightline or the dark line flows on the screen.

The inventors of the present invention found the problem associated withthe polarity inversion of the voltage applied on another liquid crystalpanel in the display apparatus configured by assembling a matrix-typeliquid crystal panel with the another display panel. The problem is thatthe polarity inversion causes fluctuation in the voltage applied on thepixel electrode, thereby causing a severe deterioration of displayquality.

SUMMARY OF THE INVENTION

An object of the present invention is to realize a method of driving adisplay apparatus and a display apparatus, with which display qualitydeterioration caused by the bright line or the dark line can beprevented.

A method according to the present invention is for driving a displayapparatus having an image display section for displaying a screen bycontrolling pixels in accordance with image data per vertical period,the pixels arranged in matrix, and a liquid crystal panel having anelectrode pair sandwiching a liquid crystal layer therebetween, theimage display section and the liquid crystal panel assembled together.In order to attain the object, the method includes the step of invertingpolarity of a voltage to be applied on the electrode pair once insubstantially one or more vertical periods.

With this method, the occurrence of a bright line or a dark line isreduced to once in substantially one vertical period of the imagedisplay means or in one or more vertical periods. Thus, this reduces anumber of the bright lines or dark lines, compared with the conventionalarrangement in which a plurality of the bright lines or dark linesappear in one vertical period. This improves display quality. Further,because the occurrence of the polarity inversion is reduced, it ispossible to reduce power consumption caused by the polarity inversion.As a result, this allows reduction of an overall power consumption.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically illustrating a display apparatusaccording to a first exemplary embodiment of the present invention.

FIG. 2 is a view illustrating waveforms of applied voltage in thedisplay apparatus according to the first exemplary embodiment.

FIG. 3 is a block diagram schematically illustrating a display apparatusaccording to second exemplary embodiment of the present invention.

FIG. 4 is a view illustrating an example of waveforms of appliedvoltages in the display apparatus according to the second exemplaryembodiment.

FIG. 5 is a view illustrating another example of waveforms of appliedvoltages in the display apparatus in the second exemplary embodiment.

FIG. 6 is a view illustrating another example of waveform of appliedvoltages in the display apparatus according to the second exemplaryembodiment.

FIG. 7 is a block diagram schematically illustrating a display apparatusaccording to a third exemplary embodiment of the present invention.

FIG. 8 is a view illustrating waveform of applied voltages in a displayapparatus according to the third exemplary embodiment.

FIG. 9 is a block diagram schematically illustrating a display apparatusaccording to a fourth exemplary embodiment of the present embodiment.

FIG. 10 is a view illustrating waveforms of applied voltages and a videosignal in the display apparatus according to the fourth exemplaryembodiment.

FIG. 11 is a cross sectional view illustrating a display apparatusaccording to a modification of the fourth exemplary embodiment.

FIG. 12 is a cross sectional view illustrating a conventional liquidcrystal display apparatus for dual use in displaying 2-D/3-D image. Theconventional liquid crystal display apparatus in FIG. 12 is displaying a3-D image.

FIG. 13 is a cross sectional view illustrating the conventional liquidcrystal display apparatus for dual use in displaying 2-D/3-D image. Theconventional liquid crystal display apparatus in FIG. 13 is displaying a2-D image.

FIG. 14 is a view illustrating waveforms of applied voltages in thedisplay apparatus illustrated in FIGS. 12 and 13.

FIG. 15 is a waveform of applied voltages and video signals in thedisplay apparatus illustrated in FIGS. 12 and 13.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

An exemplary embodiment (hereinafter, present embodiment in “FirstEmbodiment”) of a display apparatus according to the present inventionis described below, referring to FIGS. 1 and 2.

FIG. 1 is a block diagram schematically illustrating an arrangement ofthe display apparatus of the present embodiment. As illustrated in FIG.1, the display apparatus of the present embodiment is provided with amatrix-type liquid crystal panel 1, a switching liquid crystal panel 2,a video signal control circuit 3, a scanning electrode control circuit4, a control circuit 5, a switching voltage generating circuit 6, andpower source circuits 7 and 8.

The matrix-type liquid crystal panel 1 is, e.g., an active matrix typeliquid crystal panel. The matrix-type liquid crystal panel 1 isconfigured such that first (1st) to Nth scanning lines and first (1st)to Mth signal lines are arranged to cross each other (i.e. in a matrix).In each region segmented with the scanning lines and the signal lines, apixel section (not illustrate) is formed. In the pixel section, apolarizer 111, a counter electrode 112, a liquid crystal layer 113, apixel electrode 114 and a polarizer 115 are arranged in lamination inthis order as illustrated in FIG. 12. In other words, the counterelectrode 112 and the pixel electrode 114 constitute an electrode pair,sandwiching the liquid crystal layer 113 therebetween.

The pixel electrode 114 of each pixel section is connected with anactive element (not illustrated). An example of the active element is athin film transistor (TFT). The active element is connected with thescanning line and the signal line. The active element is turned ON/OFFin accordance a scanning signal inputted from the scanning line. Whenthe active element in an ON state, the active element supplies, to thepixel electrode 114, a video signal inputted from the signal line.

The scanning electrode control circuit 4 is for outputting the scanningsignal to an N number of scanning lines, the scanning signal controllingthe ON and OFF of the active element of the matrix-type liquid crystalpanel 1. The scanning electrode control circuit 4 is connected with thepower source circuit 7, which supplies power to the scanning electrodecontrol circuit 4.

Moreover, the scanning electrode control circuit 4 is connected with thecontrol circuit 5, and receives a vertical display start signal and ahorizontal synchronizing signal outputted from the control circuit 5. Ifit receives the vertical display start signal, the scanning electrodecontrol circuit 4 will output, to the 1st scanning line, the scanningsignal that is to turn ON the active element connected to the 1stscanning line. After that, at a timing of the horizontal scanning signalthe scanning electrode control circuit 4 outputs, to the 1st scanningline, a scanning signal that is to turn OFF the active element. At thesame time the scanning electrode control circuit 4 outputs, to thesecond (2nd) scanning line, the scanning signal that is to turn ON theactive element. In this way, the scanning electrode control circuit 4outputs the scanning signals to the 1st to Nth scanning lines at thetiming of the horizontal synchronizing signal.

The video signal control circuit 3 is for supplying the video signal(image data) to the pixel electrodes of the matrix-type liquid crystalpanel 1 via an M number of signal lines. Specifically speaking, thevideo signal control circuit 3 applies, on the pixel electrodes, avoltage that corresponds to the video signal. The video signal controlcircuit 3 is connected with the power source circuit 7. The power sourcecircuit 7 supplies power to the video signal control circuit 3.

Moreover, the video signal control circuit 3 is connected with thecontrol circuit 5. The video signal control circuit 3 receives thevertical display start signal and the horizontal synchronizing signaloutputted from the control circuit 5. If it receives the verticaldisplay start signal the video signal control circuit 3 will output, to1st to Mth signal lines, a video signal for a first (1st) row. Next, ata timing of the horizontal scanning signal, the video signal controlcircuit 3 outputs a video signal for a second (2nd) row. In this way,the video signal control circuit 3 sequentially outputs, to the 1st toMth signal lines, video signal for 1st to Nth rows at the timing of thehorizontal synchronizing signal.

The control circuit 5 is for generating the vertical display startsignal and the horizontal synchronizing signal and outputting thesignals to the video signal control circuit 4 and the scanning electrodecontrol circuit 3.

The switching liquid crystal panel 2 is assembled together with thematrix-type liquid crystal panel 1. The switching liquid crystal panel 2is for switching over, e.g., 2-dimensional (2-D) image display and3-dimensional (3-D) image display by a voltage applied thereon. Here,the voltage may be 0 V. The switching liquid crystal panel 2 is, asillustrated in FIG. 12, provided with a patterned retardation film 121,an upper electrode 122, a liquid crystal layer 123, a lower electrode124, and a polarizer 125, which are arranged in lamination in thisorder. In other words, the upper electrode 122 and the lower electrode124 constitute an electrode pair sandwiching the liquid crystal layer123.

The all pixel sections of the matrix-type liquid crystal panel 1 includethe patterned retardation film 121, the upper electrode 122, the liquidcrystal layer 123, the lower electrode 124, and the polarizer 125.Therefore, it is possible to apply the voltage on an entire screen viathe upper electrode 122 and the lower electrode 124 at once.

The switching liquid crystal panel 2 is connected with the switchingvoltage generating circuit 6 for generating a voltage that is to beapplied for switching over the display. The voltage generated by theswitching voltage generating circuit 6 is applied between the upperelectrode 122 and the lower electrode 124. In this embodiment, it is putthat for performing the 2-D display, the voltage is applied on theswitching liquid crystal panel 2, meanwhile, for performing the 3-Ddisplay, no voltage is applied on the switching liquid crystal panel 2.

The switching voltage generating circuit 6 generates the voltage that isto be applied on the switching liquid crystal panel 2. In accordancewith a 2-D/3-D display switching signal, the switching voltagegenerating circuit 6 switch over whether or not the voltage is appliedon the switching liquid crystal panel 2. In other words, the switchingvoltage generating circuit 6 is control means for controlling driving ofthe switching liquid crystal panel 2.

Further, the switching voltage generating circuit 6 switches over apolarity of the voltage to be applied. In order to switch over thepolarity of the voltage, the switching voltage generating circuit 6changes the voltages to be applied respectively on the upper electrode122 and the lower electrode 124 of the switching liquid crystal panel 2.Specifically speaking, the switching voltage generating circuit 6decreases the voltage for the upper electrode 122 while increasing thevoltage for the lower electrode 124, in order to invert the polarityfrom positive to negative. To the contrary, in order to invert thepolarity from negative to positive, the switching voltage generatingcircuit 6 increases the voltage for the upper electrode 122 whiledecreasing the voltage for the lower electrode 124. By applyingdifferent voltages on the upper electrode 122 an the lower electrode124, a necessary power source voltage can have a smaller range, therebyattaining reduction of power consumption.

The switching voltage generating circuit 6 is provided with anoscillator circuit 61 and a buffer circuit 62.

The oscillator circuit 61 is for generating an inversion timing signalthat indicates the timing for the polarity inversion of the voltage tobe applied on the switching liquid crystal panel 2.

The oscillator circuit 61 receives the 2-D/3-D display switching signalfrom outside. If a 2-D/3-D display switching signal representing the 2-Ddisplay is inputted into the oscillator circuit 61, the oscillatorcircuit 61 oscillates at a predetermined timing and generates theinversion timing signal representing the timing. The oscillator circuit61 applies, via the buffer circuit 62, the voltage onto the upperelectrode 122 and the lower electrode 124 of the switching liquidcrystal panel 2, the polarity of the voltage being inverted inaccordance with the inversion signal thus generated.

On the other hand, if a 2-D/3-D display switching signal representingthe 3-D display is inputted into the oscillator circuit 61, theoscillator circuit 61 performs no oscillation (i.e. does not generatethe inversion timing signal) and applies no voltage on the upperelectrode 122 and the lower electrode 124 of the switching liquidcrystal panel 2.

The buffer circuit 62 is for applying a predetermined voltage on theswitching liquid crystal panel 2. The buffer circuit 62 is connected tothe oscillator circuit 61 and the power source circuit 8. If theinversion signal is inputted in the buffer circuit 62 from theoscillator circuit 61, the buffer circuit 62 will receive power suppliedfrom the power source circuit 8, and output a predetermined voltage tothe switching liquid crystal panel 2. In accordance with the inversiontiming signal from the oscillator circuit 61, the buffer circuit 62inverts the polarity of the voltage that the buffer circuit 62 is tooutput. If no signal is inputted from the oscillator 61 into the buffercircuit 62, the buffer circuit 62 does not output the voltage to theswitching liquid crystal panel 2.

As described above, if the switching voltage generating circuit 6receives the 2-D/3-D display switching signal representing the 2-Ddisplay, the switching voltage generating circuit 6 will generate theinversion signal and output the inversion signal to the switching liquidcrystal panel 2, the polarity of the inversion signal inverted inaccordance with the inversion timing signal. On the other hand, if theswitching voltage generating circuit 6 receives the 2-D/3-D displayswitching signal representing the 3-D display, the switching voltagegenerating circuit 6 will output no voltage to the switching liquidcrystal panel 2.

Next, a driving method of the matrix-type liquid crystal panel 1 and theswitching liquid crystal panel 2 is described.

The oscillator circuit 61 of the switching voltage generating circuit 6in the present embodiment generates the inversion timing signal once avertical period of the matrix-type liquid crystal panel 1.

More specifically, the oscillator circuit 61 generates the inversiontiming signal at a frequency that is substantially ½ of a frequencycorresponding to one vertical period of the matrix-type liquid crystalpanel 1. FIG. 2 illustrates a waveform of a voltage applied on thematrix-type liquid crystal panel 1 and the switching liquid crystalpanel 2.

As illustrated in FIG. 2, the polarity inversion of the voltage appliedon the switching liquid crystal panel 2 is carried out once within onevertical period of the matrix-type liquid crystal panel 1. That is, anumber of times the polarity inversion in the switching liquid crystalpanel 2 takes place in one vertical period is less than that in aconventional driving method illustrated in FIG. 14.

This makes it possible to reduce a number of bright lines or dark linescompared with a conventional arrangement, the bright lines and darklines caused respectively due to excess charging or insufficientcharging of the pixel electrode as a result of the polarity inversion ofthe voltage applied on the switching liquid crystal panel 2. Thisattains improvement of the display quality.

Moreover, because the cycle of the polarity inversion period of thevoltage of the switching liquid crystal pane 2 becomes longer than theconventional arrangement, a current consumption required by theswitching voltage generating circuit 6 can be reduced.

Even though the present embodiment is arranged such that the switchingvoltage generating circuit 6 generates the inversion timing signal oncein one vertical period of the matrix-type liquid crystal panel 1.However, the present invention is not limited to this. The switchingvoltage generating circuit 6 may be arranged such that it generates theinversion timing signal once in two or more vertical periods of thematrix-type liquid crystal panel 1. With this arrangement, the polarityinversion of the voltage applied on the switching liquid crystal panel 2is carried out once within two or more vertical periods of thematrix-type liquid crystal panel 1. As a result, the bright line or thedark line appear once in two or more vertical period. This renders thebright line or the dark line less visible and harder to recognize.

Second Embodiment

The first embodiment is arranged such that the vertical display startsignal is generated by the control circuit 5 of the matrix-type liquidcrystal panel 1, and the inversion timing signal representing the timingof the polarity inversion of the voltage applied on the switching liquidcrystal panel 2 is generated by the switching voltage generating circuit6. That is, the vertical display start signal and the inversion timingsignal are generated in different configuration blocks.

In this arrangement, there is a possibility that a pulse of the verticaldisplay start signal and a pulse of the inversion timing signal wouldhave a time lag, which would be different in each vertical period. Inother words, there is a possibility that the inversion point of theinversion of the switching liquid crystal panel 2 would be changed withrespect to the vertical display start signal. If the time lag is changedin each vertical period, the bright line or the dark line flows on thedisplayed screen. A second exemplary embodiment (hereinafter, referredto as the present embodiment in “Second Embodiment”) has a preferablearrangement that avoids this problem.

A display apparatus according to the present embodiment is describedbelow, referring to FIGS. 3 to 6. For the sake of easy explanation,sections having the same functions as those described in the firstembodiment are labeled in the same manner and their explanation isomitted here.

FIG. 3 is a block diagram illustrating an arrangement of the displayapparatus according to the present embodiment. The present embodiment isdifferent from the first embodiment in that the display apparatus of thesecond embodiment is provided with a control circuit 15 in lieu of thecontrol circuit 5, and a switching voltage generating circuit 16 in lieuof the switching voltage generating circuit 6, and the control circuit15 and the switching voltage generating circuit 16 are connected witheach other.

The control circuit 15 generates a horizontal synchronizing signal and avertical display start signal for driving a matrix-type liquid crystalpanel 1, and an inversion timing signal representing a timing ofpolarity inversion of a voltage applied on the switching liquid crystalpanel 2. The control circuit 15 outputs, to the switching voltagegenerating circuit 16, the inversion timing signal that the controlcircuit 15 generated. A method of generating the inversion timing signalby the control circuit 15 is later described.

The switching voltage generating circuit 16 generates the voltage to beapplied on the switching liquid crystal panel 2, and switches over, inaccordance with a 2-D/3-D display switching signal inputted in theswitching voltage generating circuit 16, whether or not the voltage isto be applied on the switching liquid crystal panel 2. Further, inaccordance with the inversion timing signal inputted in the switchingvoltage generating circuit 16 from the control circuit 15, the switchingvoltage generating circuit 6 switches over polarity of the voltage to beapplied.

The switching voltage generating circuit 16 is provided with a flip-flop63 and a buffer circuit 62.

The flip-flop 63 receives the 2-D/3-D display switching signal fromoutside, and the inversion timing signal from the control circuit 15.

If a 2-D/3-D display switching signal representing 3-D display isinputted therein, the flip-flop 63 will not perform the voltageapplication that applies the voltage on the switching liquid crystalpanel 2 via the buffer circuit 62.

On the other hand, if a 2-D/3-D display switching signal representing2-D display is inputted therein, the flip-flop 63 will perform thevoltage application, that is, apply the predetermined voltage on theswitching liquid crystal pane 2 via the buffer circuit 62. In performingthe voltage application, the flip-flop 63 inverts the polarity of itsoutput voltage in accordance with the inversion timing signal inputtedin the flip-flop 63.

As described above, if the 2-D/3-D display switching signal representingthe 2-D display is inputted therein, the switching voltage generatingcircuit 16 will output, to the switching liquid crystal panel 2, thevoltage whose polarity has been inverted in accordance with a pulse ofthe inversion timing signal from the control circuit 15. That is, theswitching voltage generating circuit 16 and the control circuit 15 arecontrol means for controlling driving of the switching liquid crystalpanel 2.

In the following, Examples of the inversion timing signal generated bythe control circuit 15 are described, referring to FIGS. 4 to 6.Illustrated in FIGS. 4 to 6 are waveforms of signals and voltages in therespective Examples. The signals and voltages are: vertical displaystart signals; voltages applied on the matrix-type liquid crystaldisplay panel 1; inversion timing signals; and voltages applied on theswitching liquid crystal panel 2.

Example 1

The control circuit 15 generates an inversion timing signal that is insynchronism with a cycle (i.e. vertical cycle) of a vertical displaystart signal. The control circuit 15 outputs to the switching voltagegenerating circuit 16 the thus generated inversion timing signal. Thecontrol circuit 15 generates both of the vertical display start signaland the inversion timing signal. Therefore, cycles of the verticaldisplay start signal and the inversion timing signal can be the same.

FIG. 4 illustrates waveforms of the signals and voltages in the presentExample.

As illustrated in FIG. 4, cycles of the vertical display start signaland the inversion timing signal are in synchronism. Thus, polarity ofthe voltage applied on the switching liquid crystal panel 2 is invertedonce in one vertical period. Therefore, the bright line or the dark lineappears once on the displayed screen. A number of the bright line or thedark line is less in the present Example than the conventionalarrangement.

Moreover, because the cycles of the vertical display start signal andthe inversion timing signal are in synchronism, a time lag between thesesignals is constant in each vertical period. Therefore, the bright lineor the dark line appears on a constant position on the displayed screen,but will not flow over the displayed screen. As a result, it renders thebright line or the dark line less visible and harder to recognize. Thisfurther improves the display quality of the displayed screen.

Example 2

The control circuit 15 generates an inversion timing signal that is insynchronism with an N-time-greater cycle than the cycle (i.e. verticalcycle) of the vertical display start signal. The control circuit 15outputs to the switching voltage generating circuit 16 the thusgenerated inversion timing signal.

FIG. 5 illustrates waveforms of the signals and voltages where N=2.

Because the N-times-greater cycle (in FIG. 5, a double cycle) of thevertical display start signal is in synchronism with the cycle of theinversion timing signal, the polarity of the voltage applied on theswitching liquid crystal panel 2 is inverted once in an N number ofvertical periods (in FIG. 5, two vertical period). Thus, the bright lineor the dark line appears once on the displayed screen in the N number ofvertical period (in FIG. 5 two vertical period). This renders the brightline or the dark line less visible.

Moreover, because the cycle of polarity inversion of the voltage appliedon the switching liquid crystal panel 2 is longer than in Example 1, itis possible to attain further reduction of the current consumptionrequired by the switching voltage generating circuit 16.

Further, because the N-time-greater cycle of the vertical display startsignal and the cycle of the inversion timing signal are in synchronism,a time lag between these signals is constant in each vertical period inwhich the polarity inversion of the voltage applied on the switchingliquid crystal pane 2 is carried out. Therefore, the bright line or thedark line appears on a constant position on the displayed screen.Consequently, as in Example 1, the bright line or the dark line will notflow over the displayed screen and becomes less visible and harder torecognize.

Example 3

The control circuit 15 generates an inversion timing signal that is insynchronism with a cycle (i.e. vertical cycle) of a vertical displaystart signal. The control circuit 15 outputs the thus generatedinversion timing signal to the switching voltage generating circuit 16in such a manner that a pulse of the inversion timing signal is withinthe vertical blanking period of the matrix-type liquid crystal panel 1.

The vertical blanking period is that part of one vertical period inwhich no writing (i.e. supply) of the video signal is carried out withrespect to all the pixel electrodes 114. Therefore, all the activeelements connected with the pixel electrodes 114 are in an OFF stateduring the vertical blanking period. The control circuit 15 cancalculate out the vertical blanking period easily from the verticaldisplay start signal and the horizontal synchronizing signal. Theinversion timing signal that is in synchronism with the vertical cycleis outputted from the control circuit 15 in such a manner that the pulseof the inversion timing signal is within the vertical blanking periodwhich is a period between (a) output of a horizontal synchronizingsignal corresponding to pixel electrodes 114 of the Nth row and (b)output of a horizontal synchronizing signal corresponding to pixelelectrodes 114 of the 1st row.

The horizontal synchronizing signal for the 1st row is a horizontalsynchronizing signal that is firstly outputted after the pulse of thevertical display start signal is outputted. The horizontal synchronizingsignal for the Nth row is a horizontal synchronizing signal that isoutputted Nthly after the pulse of the vertical display start signal isoutputted.

FIG. 6 is a waveform of the signals and voltages in the present Example.

As illustrated in FIG. 6, the polarity inversion timing of the voltageapplied on the switching liquid crystal panel 2 is within the verticalblanking period of the matrix-type liquid crystal panel 1. Therefore,the fluctuation of the video signal as illustrated in FIG. 15 occurswhen the active element is in the OFF state. Therefore, excess chargingand insufficient charging of the pixel electrode will not occur. Thus,no bright line nor dark line will be appear in the displayed screen.This allows to display the screen with higher display quality.

Third Embodiment

A third exemplary embodiment (hereinafter, present embodiment in “ThirdEmbodiment”) is described below. A display apparatus according to thepresent embodiment is described below, referring to FIGS. 7 and 8. Forthe sake of easy explanation, sections having the same functions asthose described in the embodiments discussed above are labeled in thesame manner and their explanation is omitted here.

FIG. 7 is a block diagram illustrating an arrangement of the displayapparatus of the present embodiment. The present embodiment is differentfrom the embodiment illustrated in FIG. 3 in that a control circuit 15outputs a vertical display start signal (which the control circuit 15outputs to a scanning electrode control circuit 4) to a switchingvoltage generating circuit 16, instead of outputting the inversiontiming signal to the switching voltage generating circuit 16.

In other words, the control circuit 15 outputs, to the switching voltagegenerating circuit 16, the vertical display start signal as an inversiontiming signal.

FIG. 8 illustrates waveforms of signals and voltages in the presentembodiment. As illustrated in FIG. 8, a rise point of the inversiontiming signal (vertical display start signal) is within a verticalblanking period. Therefore, the timing of the polarity inversion of avoltage applied on a switching liquid crystal panel 2 is within thevertical blanking period. With this arrangement, as in Example 3, excesscharging and insufficient charging of the pixel electrode will notoccur. Thus, no bright line nor dark line will appear on the displayedscreen. This allows to display the screen with higher display quality.

Moreover, with the control circuit 15, it is possible that one of thevertical display start signal and the inversion timing signal is used toserve as both of the signal. With this arrangement, it is possible tosimplify a circuit configuration of the control circuit 15.

Fourth Embodiment

Fourth exemplary embodiment (hereinafter, the present embodiment in“Fourth Embodiment”) is an arrangement that makes it possible to furthersimplify circuit components. A display apparatus according to thepresent embodiment is described below, referring to FIG. 9. For the sakeof easy explanation, sections having the same functions as thosedescribed in the embodiments discussed above are labeled in the samemanner and their explanation is omitted here.

FIG. 9 is a block diagram illustrating an arrangement of the displayapparatus of the present embodiment. The present embodiment is differentfrom the embodiment illustrated in FIG. 7 in that a power source circuit17 which supplies power both to a matrix-type liquid crystal panel 1 anda switching liquid crystal panel 2 is provided, instead of providing thepower source circuit 7 for the matrix-type liquid crystal panel 1 andthe power source circuit 8 for the switching liquid crystal panel 2.

The circuit component necessary for configuring a power source circuitcan be reduced significantly by adopting the arrangement in which thesingle power source circuit 17, which is used both for the matrix-typeliquid crystal panel 1 and the switching liquid crystal panel 2, isprovided. Thus, it is possible to simply a driving circuit for thematrix-type liquid crystal panel 1 and the switching liquid crystalpanel 2.

The present embodiment is arranged such that, as illustrated in FIG. 9,the display apparatus is provided with a control circuit 15 and aswitching voltage generating circuit 16, and that the control circuit 15outputs, to the switching voltage generating circuit 16, a verticaldisplay start signal as an inversion timing signal.

However, the present embodiment is not limited to this. The presentembodiment may be arranged such that the display apparatus is providedwith the control circuit 5 and a switching voltage generating circuit 6as in the first embodiment, or that the control circuit 15 outputs theinversion timing signal and the vertical display start signalrespectively as in the second embodiment. Even if the display apparatusis arranged as such, it is still possible to attain the reduction of thecircuit components by utilizing a single power circuit for both thepanels.

Fifth Embodiment

An fifth exemplary embodiment (hereinafter, present embodiment in “FifthEmbodiment”) is described below, referring to FIG. 10. A displayapparatus according to the present embodiment is configured (i.e.apparatus-wise) as in the embodiment illustrated in FIG. 1. Therefore,explanation on the configuration of the present embodiment is omittedhere.

In the first embodiment, the switching liquid crystal panel 2 is drivenin such a manner that the voltage applied on the upper electrode 122 andthe lower electrode 124 (cf. FIG. 12) is inverted. To the contrary, inthe present embodiment, a switching liquid crystal panel 2 is driven insuch a manner that a direct current (DC) voltage is applied on an upperelectrode 122 located between the switching liquid crystal panel 2 and amatrix-type liquid crystal panel 1 and only a lower electrode 124 thatis a counter electrode for the upper electrode 122, is subjected topolarity inversion.

FIG. 10 illustrates a waveform of a video signal when the switchingliquid crystal panel 2 is driven in such a manner that the polarityinversion is carried out only for the lower electrode 124. Asillustrated in FIG. 10, the voltage applied on the upper electrode 122is affected and fluctuated by the polarity inversion of the voltageapplied on the lower electrode 124. This is due to capacity couplingoccurred between the upper electrode 122 and the lower electrode 124.Because the upper electrode 122 has a sufficiently small resistance andthus a current supplying capability to the upper electrode 122 issufficient, the fluctuation occurred in the upper electrode 122 issmaller than the fluctuation occurred in the lower electrode 124.Therefore, a fluctuation amount of the video signal in the matrix-typeliquid crystal panel 1 due to the capacity coupling occurred between theupper electrode 122 and a pixel electrode 114 of the matrix-type liquidcrystal panel 1 is small.

As a result, it is possible to attain reduction in an amount of excesscharging or insufficient charging (which occurs when the polarityinversion is carried out) of the pixel electrode 114 of the matrix-typeliquid crystal panel 1. (i.e. it is possible to alleviate the excesscharging or insufficient charging). Therefore, a difference betweenbrightness of the bright line or dark line on the displayed screen andbrightness other area of the screen than the bright line or dark linebecomes small. Thus, the bright line or dark line becomes less visibleand harder to recognize. This improves the display quality of displayedscreen.

The present embodiment may be applied together with the first to fourthembodiments, respectively or in combination. That is, the switchingliquid crystal panel 2 of the present embodiment may be arranged suchthat a DC voltage is applied the upper electrode 122 positioned betweenthe matrix-type liquid crystal panel 1 and the switching liquid crystalpanel 2 and only the lower electrode 124, which is a counter electrodeof the upper electrode 122, is subjected to the polarity inversion. Withthis arrangement, it is possible to reduce a fluctuation amount of thevideo signal in the matrix-type liquid crystal panel 1, therebyrendering the bright line or dark line on the displayed screen furtherless visible and harder to recognize.

Even though in the present embodiment the switching liquid crystal panel2 is arranged such that the DC voltage is applied on the upper electrode122 (of the switching liquid crystal panel 2) located between theswitching liquid crystal panel 2 and the matrix-type liquid crystalpanel 1, the present invention is. however, not limited to thisarrangement. The matrix-type liquid crystal panel 1 may be arranged suchthat a DC voltage is applied on its electrode located between theswitching liquid crystal panel 2 and the matrix-type liquid crystalpanel 1. That is, as illustrated in FIG. 11, the matrix-type liquidcrystal panel 1 and the switching liquid crystal panel 2 are assembledsuch that the counter electrode 112 of the matrix-type liquid crystalpanel 1 is located between the matrix-type liquid crystal panel 1 andthe switching liquid crystal panel 2. The application of the DC voltageon the counter electrode 112 of the matrix-type liquid crystal panel 1causes the pixel electrode 114 less susceptible from the polarityinversion of the voltage applied on the switching liquid crystal panel2. This reduces the amount of the excess charging and the insufficientcharging. As a result, the bright line or the dark line becomes lessvisible and harder to recognize.

Moreover, even though the above explanation discusses the case where theliquid crystal panel assembled together with the matrix-type displayapparatus is the 2-D/3-D display switching liquid crystal panel, thepresent invention is not limited to this. In other words, the liquidcrystal panel assembled together with the matrix-type display apparatusmay be any liquid crystal panel, provided that it is provided with anelectrode that can be capacity-coupled with the pixel electrode of thematrix-type display apparatus.

For example, the liquid crystal panel assembled together with thematrix-type display apparatus may be a liquid crystal display panelthat, when displaying in a first display state, it displays a screenhaving a first display region and a second display region, which aresegmented by a parallax barrier means, and on which different imagesources are displayed respective, and that it displays an image sourceon an entire screen region when displaying in a second display state.

Even though the above exemplary embodiments discusses, by way ofexample, the switching liquid crystal panel 2 is provided with twoelectrodes, namely the upper electrode 122 and the lower electrode 124,the present invention is not limited to this arrangement. The switchingliquid crystal panel 2 may be a matrix-type liquid crystal panel.

As described above, a method according to the present invention is fordriving a display apparatus having an image display section fordisplaying a screen by controlling pixels in accordance with image dataper vertical period, the pixels arranged in matrix, and a liquid crystalpanel having an electrode pair sandwiching a liquid crystal layertherebetween, the image display section and the liquid crystal panelassembled together. The method according to the present inventionincludes the step of inverting polarity of a voltage to be applied onthe electrode pair once in substantially one or more vertical periods.

Further, in addition to the above arrangement, the method according tothe present invention is preferably arranged such that the polarity ofthe voltage to be applied on the electrode pair is inverted in a cyclesame as the vertical period.

In the method, the vertical cycle of the image display apparatus and thepolarity inversion cycle of the voltage applied on the electrode pairare the same. Thus, according to the present invention, the time lagbetween the timing of the inversion of the polarity and the start pointof the vertical period of the image display means is constant in eachvertical period. In other words, the polarity inversion timing isconstant in each vertical period. With this, that position on the screenat which the bright line or the dark line occur is always the same. As aresult, the bright line or the dark line becomes less visible and harderto recognize, thereby improving the display quality.

Further, in addition to the above arrangement, the method according tothe present invention is preferably arranged such that the polarity ofthe voltage to be applied on the electrode pair is inverted in a cycle Ntimes greater than the vertical period, where N is an integer not lessthan 2.

According to the method, the dark line or the bright line, which occurswhen the polarity of the voltage applied on the liquid crystal panel isinverted, occurs only once in the N number of vertical periods.

Further, in the vertical period of the image display apparatus, thetiming of the polarity inversion is constant. In other words, thepolarity inversion timing is constant in each vertical period. Withthis, that position on the screen at which the bright line or the darkline occur is always the same. As a result, the bright line or the darkline becomes less visible and harder to recognize, thereby furtherimproving the display quality.

Moreover, in addition to the above arrangement, the method according tothe present invention is preferably arranged such that the polarity ofthe voltage to be applied on the electrode pair is inverted within avertical blanking period of the image display section.

Here, the vertical blanking period is that part of one vertical periodin which no wring of image data (that is, controlling of the pixel inaccordance with the image data) is carried out for any pixel.

According to the driving method in which the polarity inversion of thevoltage applied on the liquid crystal panel is carried out in thevertical blanking period, the excess charging of the pixel or theinsufficient charging of the pixel due to the polarity inversion neveroccurs. Thus, no bright line or dark line appears. This improves thedisplay quality.

Further, in addition to the above arrangement, the method according tothe present invention is preferably arranged such that the polarity ofthe voltage to be applied on the electrode pair is inverted insynchronism with start of the vertical period.

According to the method, the start point of the vertical period iswithin the vertical blanking period in which no writing of the imagedata is carried out for any pixel. Thus, in the method, the polarity ofthe voltage applied on the liquid crystal panel is inverted within thevertical blanking period. Thus, no bright line or dark line appears onthe displayed screen, thereby improving the display quality.

Moreover, the start point of the vertical period and the polarityinversion point of the voltage applied on the liquid crystal panel isconcurrent. This allows the display apparatus to use the samearrangement in order to control the vertical period of the image displaymeans and to control the polarity inversion timing of the voltageapplied on the liquid crystal panel. This allows simplification of thecircuit configuration of the display apparatus.

Further, in addition to the above arrangement, the method according tothe present invention is preferably arranged to include the step ofapplying a direct current voltage on that electrode of the electrodepair which is located between the image display section and the liquidcrystal panel.

According to the method, the DC current is applied on that electrode ofthe electrode pair which is located between the image display apparatusand the liquid crystal panel. Because of this, a potential of the otherelectrode of the electrode pair is changed when the polarity of thevoltage applied on the electrode pair is inverted (the other electrodeis located on that surface of the liquid crystal panel which does notface the image display apparatus). When this occurs, capacity couplingbetween the electrode and the other electrode of the electrode paircauses the electrode to be affected from the potential change occurredin the other electrode. However, because the DC current is appliedthereon, the electrode located between the image display apparatus andthe liquid crystal panel is generally less susceptible from the otherelectrode potential, and thus the amount of the potential change issmall. Therefore, the amount of the change in the image data of theimage display means due to the polarity inversion of the voltage appliedon the liquid crystal panel is small.

As a result, the difference between the brightness of the bright line orthe dark line occurred when the polarity inversion occurs and thebrightness of the other region of the screen becomes small. This causesthe bright line or the dark line to be less visible and harder torecognize. This further improves the display quality of the displayedscreen.

Further, in addition to the above arrangement, the method is preferablyarranged such that the image display section comprises a liquid crystallayer and an electrode pair sandwiching the liquid crystal layer, andthe method comprises the step of applying a direct voltage on thatelectrode of the electrode pair of the image display section which islocated between the image display section and the liquid crystal panel.

According to the method, the DC current is applied on that electrode ofthe electrode pair of the image display apparatus which is locatedbetween the image display apparatus and the liquid crystal panel. Thus,this electrode is less susceptible from the change in the potential ofthe other electrode of the electrode pair of the image displayapparatus. Therefore, the amount of the potential change of thiselectrode is small. Therefore, that other electrode of the electrodepair of the image display apparatus which is located on that surface ofthe image display apparatus which does not face the liquid crystal panelbecomes less susceptible from the influence of the potential inversionof the voltage applied on the liquid crystal panel. As a result, theamount of the excess charging or the insufficient charging is reduced.With this, the amount of change in the image data of the image displayapparatus due to the polarity inversion of the voltage applied on theliquid crystal panel becomes small. Consequently, the bright line or thedark line occurred when the polarity inversion is carried out becomesfurther less visible and harder to recognize.

Furthermore, a display apparatus according to the present invention isprovided with a control circuit (control means, control section), whichrealizes any one of the methods of driving.

According to the arrangement, it is possible to prevent display qualitydeterioration caused by the bright line or the dark line.

Further, according to the above arrangement, the display apparatusaccording to the present invention is preferably arranged such that apower source is used for applying the voltage in accordance with theimage data in the image display section and for applying the voltage onthe electrode pair of the liquid crystal panel.

With this arrangement, it is sufficient to provide one power source bothfor the image display apparatus and the liquid crystal panel. Thisallows circuit simplification.

As described above, the method of driving the display apparatus and thedisplay apparatus according to the present invention make it possible toreduce the influence given on the image display means from the polarityinversion of the voltage applied on the liquid crystal panel. Therefore,the method and the display apparatus are suitably applicable to and as adisplay apparatus provided with a plurality of liquid crystal panels.

The invention being thus described, it will be obvious that the same waymay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A method of driving a display apparatus comprising: providing animage display section for displaying a screen by controlling pixels inaccordance with image data per vertical period, the pixels arranged inmatrix, and providing a liquid crystal panel for switching between a 2Ddisplay and a 3D display of the apparatus so as to comprise an electrodepair sandwiching a liquid crystal layer therebetween, the image displaysection and the liquid crystal panel assembled together, so that theimage display section includes a first liquid crystal layer and theliquid crystal panel includes a second liquid crystal layer spaced apartfrom the first liquid crystal layer; wherein the image display sectionand the liquid crystal panel are proximate to each other and are facingeach other; and applying an inversion timing signal for invertingpolarity of a voltage to be applied on the electrode pair included inthe liquid crystal panel, said liquid crystal panel used for switchingbetween a 2D display and a 3D display synchronized with the rising edgeof the inversion timing signal, the inversion timing signal occurringonce in two or more vertical periods of the image display section.
 2. Amethod as set forth in claim 1, wherein: the polarity of the voltage tobe applied on the electrode pair is inverted in a cycle N times greaterthan the vertical period, where N is an integer not less than
 2. 3. Amethod as set forth in claim 1 wherein: the polarity of the voltage tobe applied on the electrode pair is inverted within a vertical blankingperiod of the image display section.
 4. A method as set forth in claim 1wherein: the polarity of the voltage to be applied on the electrode pairis inverted in synchronism with start of the vertical period.
 5. Amethod as set forth in claim 1, comprising the step of: applying adirect current voltage on that electrode of the electrode pair which islocated between the image display section and the liquid crystal panel.6. A method as set forth in claim 1 wherein: the image display sectioncomprises a liquid crystal layer and an electrode pair sandwiching theliquid crystal layer; the method further comprising applying a directvoltage on that electrode of the electrode pair of the image displaysection which is located between the image display section and theliquid crystal panel.
 7. A display apparatus comprising an image displaysection for displaying a screen by controlling pixels in accordance withimage data per vertical period, the pixels arranged in matrix, and aliquid crystal panel having an electrode pair sandwiching a liquidcrystal layer therebetween for switching between a 2D display and a 3Ddisplay, the image display section and the liquid crystal panelassembled together, wherein the image display section includes a firstliquid crystal layer and the liquid crystal panel includes a secondliquid crystal layer spaced apart from the first liquid crystal layer;wherein the image display section and the liquid crystal panel areproximate to each other and are facing each other; and a control sectionfor inverting by applying an inversion timing signal, once in two ormore vertical periods of the image display section, polarity of avoltage applied on the electrode pair included in the liquid crystalpanel, said liquid crystal panel used for switching between a 2D displayand a 3D display synchronized with the rising edge of the inversiontiming signal.
 8. A display apparatus as set forth in claim 7, wherein:a power source is used for applying the voltage in accordance with theimage data in the image display section and for applying the voltage onthe electrode pair of the liquid crystal panel.
 9. A display apparatusas set forth in claim 7, wherein: the control section controls (a) aninversion timing of the polarity of the voltage to be applied on theelectrode pair, and (b) a start timing of each vertical period.
 10. Adisplay apparatus as set forth in claim 9, wherein: the control sectionsynchronizes the inversion timing and the start timing.
 11. The methodof claim 1, wherein the image display section and the liquid crystalpanel are proximate and parallel to each other, so that the imagedisplay section includes a first liquid crystal layer and the liquidcrystal panel includes a second liquid crystal layer spaced apart fromthe first liquid crystal layer.
 12. The display apparatus of claim 7,wherein the image display section and the liquid crystal panel areproximate and parallel to each other, so that the image display sectionincludes a first liquid crystal layer and the liquid crystal panelincludes a second liquid crystal layer spaced apart from the firstliquid crystal layer.